Jeff,
I am new to this forum and to the headfi equipment and was in the same boat.
My setup: Macbook Pro, Cardas Clear USB cable, New Sennheiser HDVD800 and HD800.
Tried Amara, Fidelia and Audirvana Plus 1.46 and 1.4.9.7 just installed.
To my ears Audirvana Plus 1.4.9.7 is outstanding!!! A very nice improvement over v.1.46. For me it was the best $75 I ever spent.
I have been searching for the best setup for my HD800 headphones, and I feel like I am getting closer.
Still burning in my HDVD 800 and waiting for my Cardas Clear balanced 4 pin cables for my HD800.
It would be great to hear from anybody else with the similar setup.
The members of this forum and Headfi are truly a wealth of knowledge!
Thanks guys.